The Frequency of Earthquakes
SINCE 1843 an average of 575 earthquakes a year has been known to occur. Mallet has collected the records of 6,830 earthquakes which took place over a period of 3,456 years previous to 1850; but 3,240 of these occurred during the last fifty years. It seems, therefore, that our earth is almost constantly shaking at some point, and no part of the world is entirely free from tremors of some degree. Professor Milne has recently urged that the study of earthquakes should receive more attention in countries little subject to their visitations. Such countries may at long intervals be shaken by earthquakes of a severe character, and it is suggested that even the stable ground of England may not be secure against disturbance by convulsions as calamitous as that which suddenly swept away 60,000 of the inhabitants of Lisbon in 1755.—Exchange.